This invention relates to an antenna, in particular, to an antenna built in an electronic apparatus, such as a personal computer, a printer, a copying machine, an audio-visual apparatus or the like.
Recently, a wireless local area network (LAN) system has come to be used in various places such as an (large scale) office, a hot spot service area, a school, a firm, a home and so on. Then, there is a demand to connect not only computers but also various electronic apparatus such as a copy machine, a projector, a printer, audio-visuals including a television set and/or a video recorder, or the like, to the wireless LAN system. To achieve this, a technique referred to as UWB (Ultra Wideband) has been proposed. The UWB can transmit large size data such as extended definition (moving) picture data at a high speed (e.g. 480 Mbps in maximum).
For the UWB, a frequency range from 3.1 to 10.6 GHz is supposed to be used as of December 2003. Accordingly, an antenna functioning over a very wide or broad band is necessary for the UWB. Furthermore, the antenna must have a small size to be built in the electronic apparatus as mentioned above. In addition, it is desirable that the antenna has a shape like a two-dimensional shape rather than a three-dimensional shape. This is because it is easy to be built in the electronic apparatus.
However, no antenna meets the above mentioned conditions at the present time.
A discone antenna is one of well-known antennas functioning over the wide band. Such an antenna is disclosed in “ANTENNA ENGINEERING HANDBOOK” (at page 128 of the sixth impression of the first edition) edited by IEICE (Institute of Electronics, Information and Communication Engineers) and published by Ohm Co. on Sep. 30, 1991.
Though the discone antenna functions over the wide band, it has the three-dimensional shape and is hard to be built in the personal computer, the audio-visual apparatus, or the like.